EVOLUTION OF A RUMP PATCH IN ALASKAN MOOSE: AN HYPOTHESIS

Abstract

Dark rump markings in Alaskan moose (Alces alces gigas) are hypothesized to function as a rump patch. These pelage characteristics are likely an example of rapid evolution because dates for the oldest A. alces in Alaska (ca. 9,000 year ago BP) suggest a post-glacial subspeciation of moose in North America. Moreover, mitochondrial DNA shows no subspecific variability, suggesting that moose were not isolated for long periods of time by the Wisconsin ice sheet. The occurrence of a rump patch in Alaskan moose is consistent with increasing gradients of rump-patch size exhibited by mule deer (Odocoileus hemionus), and red deer and wapiti (Cervus elaphus) that inhabit increasingly more open habitats. Likewise, Alaskan moose live in more open habitat, are larger in body size, more social, and have larger, more complex antlers than conspecifics in North America that lack striking rump markings. These attributes are also correlated with larger and more conspicuous rump patches in other cervids. We believe the group cohesion hypothesis offers the most likely explanation for dark rump markings in Alaskan moose.